如何使用动态添加的内容将包含 canvas 的 ItemControl 居中

Question

我正在使用itemsControl来显示一些绑定的ItemSource内容。 因为我需要 position 一些元素而不是其他一些元素，所以 itemsControl 面板是 canvas。

我需要将整个 canvas 水平居中。 但是，canvas 尺寸不会调整。

我错过了什么？

XAML

        <ItemsControl Grid.Row="1" ItemsSource="{Binding TopologyRepresentation}" HorizontalAlignment="Center">
            <ItemsControl.ItemsPanel>
                <ItemsPanelTemplate>
                    <Canvas Width="Auto" Height="Auto"/>
                </ItemsPanelTemplate>
            </ItemsControl.ItemsPanel>
        </ItemsControl>

代码背后

        private ObservableCollection<UIElement> _TopologyRepresentation;
        public ObservableCollection<UIElement> TopologyRepresentation
        {
            get
            {
                if (_TopologyRepresentation == null)
                {
                    _TopologyRepresentation = new ObservableCollection<UIElement>();
                    _updateTopologyRepresentation();
                }
                return _TopologyRepresentation;
            }
        }

        private void _updateTopologyRepresentation()
        {
            if (CurrentTopology == null) return;

            _TopologyRepresentation.Clear();

            // Add background image
            BitmapImage bmp = new BitmapImage(new Uri(System.IO.Path.Combine(Properties.Settings.Default.ImagePath, CurrentTopology.Image),UriKind.Relative));
            Image BodyImage = new Image
            {
                Source = bmp,
                Height = bmp.Height,
                Width = bmp.Width
            };
            _TopologyRepresentation.Add(BodyImage);

            // Add sensor / actuators image-buttons
            foreach (Topology.IO tIo in CurrentTopology.Io)
            {
                IOView v = new IOView();
                v.Margin = new Thickness(tIo.ImagePos_x, tIo.ImagePos_y, 0, 0);
                IOVM vm = new IOVM(tIo);
                v.DataContext = vm;
                _TopologyRepresentation.Add(v);
            }

            RaisePropertyChanged("TopologyRepresentation");
        }